英文標題摘要及關鍵詞

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Microstructure and mechanical properties of 6082-T6 aluminum alloy joint by high speed friction stir welding

Zhang Xinmeng1, Li Jing1, Wang Beibei2, Ni Dingrui2, Xue Peng2, Ma Zongyi2

(1.CRRC Changchun Railway Vehicles Co., Ltd., Changchun 130062, China; 2. Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China).p1-4,12

Abstract6 mm thick 6082-T6 aluminum alloy plates were welded by friction stir welding at a high welding speed of 2 000 mm/min, and microstructure and mechanical properties of the joint were studied. Experimental results showed that sound FSW joints without defects in the nugget zone were achieved at a high welding speed. Discontinuous “S” line was observed in the nugget zone. Grains in the nugget zone were refined to 10 μm, and coarsening of the precipitates in the heat affected zone were significantly inhibited. The lowest hardness clearly increased to 72 HV, which reached to the similar level of the nugget zone (75 HV). In tensile test, joints fractured in the heat affected zone. Tensile strength of the joint was 262 MPa, up to 85% of the base metal, which was better than that of the joint under conventional parameters. This study showed that high welding speed friction stir welding of aluminum alloy could not only improve the mechanical properties of the joint, but also significantly improve the welding production efficiency.

Keywords:6082-T6aluminumalloy,frictionstirwelding,weldingspeed,mechanicalproperties

Effect oft8/5on fracture toughness of CGHAZ of X100 pipeline steel

Zhu Haishan1, Xu Lianyong2, Cao Jian3, Jia Lusheng1

(1.CNOOC Research Institute Ltd., Beijing 100028, China; 2. Tianjin University, Tianjin 300350, China; 3. Harbin Institute of Technology, State Key Laboratory of Advanced Welding and Joining, Harbin 150001, China).p5-12

AbstractAccording to BS 7448 standard and microscopic analysis method, thermal simulation technique was used to study the fracture toughness (CTOD) of the coarse grain zone in heat affected zone of X100 grade pipeline steel under differentt8/5. The results showed that CTOD value increased as the t8/5time increased, and microstructure was transformed from lath bainite to granular bainite. The coarse chain M-A component appeared at the grain boundary of the prior austenite att8/5=40 s, which caused a small decrease in fracture toughness. Whent8/5was 50 s, the fracture toughness continued to increase. However, the grains tended to coarsen as t8/5increased.

Keywords:X100pipelinesteel,thermalsimulation,coarsegrainzone,fracturetoughness

Numerical simulation of thermal-mechanical development of GH4169 alloy in laser additive manufacturing process

Chong Run, Guo Shaoqing, Zhang Wenyang, Li Bohong, Zhao Zijun, Huang Shuai

(AECC Beijing Institute of Aeronautical Materials, Beijing 100095, China).p13-21

AbstractIn order to solve the problem of deformation and even cracking in the laser additive manufacturing process of GH4169 alloy, a direct coupled thermo-elastoplastic finite element method was used to simulate and analyze the temperature and stress evolution during the laser additive manufacturing process of GH4169 alloy single-layer multilayer wall. The results showed that the deposition specimen underwent rapid heating and cooling during the laser additive process, and the temperature change rate exceeded 1×105℃/s. The peak temperature of the thermal cycle exceeded 2 500 ℃, and the highest temperature reached 2 876 ℃. The area scanned by laser deposition was constrained by the cooling shrinkage, which resulted in high stress. The temperature of the area scanned by the laser during the subsequent deposition increased again, which would first release the stress formed by the previous deposition, then would cause greater stress as the temperature decreased. At the moment when the deposition was over, the temperature of the part abnormally increased where the deposited layer was connected to the substrate. The residual stress of the deposition layer was dominated by tensile stress, up to 875 MPa. The stress component along the deposition direction was the largest. The residual stress of the substrate near the junction with the deposited layer reached about 800 MPa, and the residual compressive stress was distributed in the distance.

Keywords:nickel-basedsuperalloy,laseradditivemanufacturing,finiteelement,temperaturefield,stressfield

Microstructure and mechanical properties of 3003 aluminum alloy by laser welding

Fan Jikang1,2, Ni Cheng1, Xu Honglin2, Peng Yong1, Song Youmin2, Wang Kehong1

(1. Nanjing University of Science and Technology, Key Laboratory of Controlled Arc Intelligent Additive Technology, Ministry of Industry and Information Technology, Nanjing 210094, China; 2. Kunshan Huaheng Welding Co., Ltd., Kunshan 215300, Jiangsu, China)p22-25

AbstractIn order to explore the application of 3003 aluminum alloy in power battery casing and other fields, laser swing method was used to carry out welding process experiments on 1.5 mm thick 3003 aluminum alloy sheet, microstructure and mechanical properties of the welded joint were analyzed. The results showed that under surface focusing conditions, a well-formed welded joint could be obtained at 40 mm/s welding speed, 1 350 W laser power, 5 000 Hz pulse frequency, 100 Hz swing frequency and 0.3 mm swing diameter. There existed a fine-grain zone at the fusion line of the welded joint and the center of the weld. The transition area from the fusion line to the center of the weld was composed of columnar crystals and the overall microstructure of the joint was refined. The hardness of each zone of the welded joint was higher than that of the base material, the tensile strength was about 91% of that of the base material, and the elongation after fracture was about 65% of that of the base material. The fracture form of the joint was a mixed fracture of toughness and quasi-cleavage.

Keywords:3003aluminumalloy,laserswingwelding,microstructure,mechanicalproperties

Weld design of TC17 titanium alloy blade test component by linear friction welding

Yu Xueran, Chen Yunyong

(AECC Commercial Aircraft Engine Co., Ltd., Shanghai 200241, China).p26-29

AbstractBased on Goodman diagram and combined with the results of steady-state stress analysis and modal analysis, a method of assessing weak position of blade vibration was put forward in the paper. Based on the method, effects of weld height and welding angle of TC17 titanium alloy blade test component on blade vibration safety was analyzed in the paper. Besides, effects of weld height and welding angle on the vibration safety of the blade element in the first order bending mode and the first order torsion mode were also analyzed. The analysis results showed that for the first order bending mode of blade test component by linear friction welding, effects of blade welding angle and weld height on the vibration safety of blade were more than 29%, while for the first order torsion vibration safety, effects of welding angle and weld height are 227% and 392%, respectively. By analyzing effects of linear friction welds in the first order bending mode and torsion mode, the suitable welding position of TC17 titanium alloy blade test component by linear friction welding was obtained.

Keywords:TC17titaniumalloy,blade,linearfrictionwelding,weldheight,weldingangle

Ultrasonic C-scan method for characterizing brazing quality

Qi Yuefeng1, Zhang Guoqing2, Ruan Lei3, Huang Xiaomeng2, Yu Wenbo1

(1.Beijing Non-ferrous Metal and Rare Earth Research Institute, Beijing 100012, China; 2. Beijing Engineering Research Center of New Brazing Materials for Electronic Information, Beijing 100012, China; 3. Beijing Academy of Launch Vehicle Technology, Beijing 100076, China).p30-34

AbstractTo realize the overall evaluation of brazed joint quality, ensure the connection quality of finished brazed workpieces and verify the brazing process, and avoid the destructive disadvantages of traditional physical testing methods, the water immersion ultrasonic testing method was used to analyze the C-scan image, so as to realize the nondestructive, efficient and automatic evaluation of brazed joint quality. By selecting the probe, adjusting the water distance, setting the scanning mode, and using the corresponding reference block to adjust the scanning sensitivity, the test parameters were determined. The results showed that the ultrasonic C-scan results could directly characterize the quality of the brazed layer. The metallographic and EDS analysis of the areas with different echo heights verified the corresponding state of the brazed layer. At the same time, for planar workpieces, tubular workpieces and multilayer brazed workpieces, the joint state and internal defect position of brazed joint could be reflected efficiently, intuitively and comprehensively. Using the area statistical function of the software, the brazing rate was calculated according to the formula and the non-destructive and quantitative evaluation of brazing quality was realized.

Keywords:waterimmersionultrasonictesting,brazedjoint,brazingrate,C-scan

Bonding technology of high purity yttrium target

Xu Guojin1, 2, Zhang Qiaoxia1,2, Luo Junfeng1,2, Li Yongjun1,2, Teng Haitao1,2, Xiong Xiaodong1,2

(1. GRIKIN Advanced Materials Co., Ltd., Beijing 102200, China; 2. The High Purity Metal Sputtering Target Engineering Technology Research Center in Beijing, Beijing 102200, China).p35-38

AbstractTaking high purity rare earth yttrium materials, copper and 6061Al alloy materials as study objects, the soldering and diffusion welding properties of high purity rare earth yttrium targets were studied. The results indicated that the wettability of rare earth yttrium targets to In solder was poor, so it was necessary to metalize the target material to improve its soldering performance. The influence of soldering temperatures on the welding quality of rare earth yttrium targets was studied. The higher the soldering temperature was, the higher the soldering rate of targets was, which was related to the improvement of solder fluidity. The diffusion welding technology of high purity rare-earth yttrium targets and 6061Al alloy was studied. After the diffusion welding at 400 ℃ welding temperature, 110 MPa welding pressure and 3 h holding time, the diffusion depth was about 8 μm, and the welding interface was metallurgical bonding. The welding strength was up to 70 MPa, which met the high sputtering power requirements of the large size targets of 8～12 inches.

Keywords:targets,highpurityyttrium,6061Alalloy,soldering,diffusionwelding

Parameters optimization of laser transmission welding polycarbonate based on LibSVM

Huang Jiapei, Yan Tingpei, Ding Ning ,Wang Chuanyang

(Soochow University, Suzhou 215131, Jiangsu, China).p39-45

AbstractTransparent polycarbonate (PC) was selected as the experimental object and mixtures of aluminum powders and carbon powders were used as the absorbent. The support vector machine algorithm was used to perform regression analysis on the experimental data of laser transmission welding polycarbonate to obtain the theoretical optimal welding parameters. Firstly, the surface response method was used to plan the experiment program to obtain the correlation model of welding quality and welding process. Secondly, LibSVM support vector machine was used to optimize welding parameters (laser power, absorbent ratio, welding speed, surface roughness). Finally, model regression was used to predict and experimental verification was conducted. The research results showed that the best welding quality was obtained under condition of 37 W laser power, 5 mm/s welding speed, 29% aluminum powder content and 1.77 μm surface roughness. At the same time, the error between the optimized predicted value and the experimental value was small. It was of guiding significance to reduce welding cost and improve welding quality and welding efficiency.

Keywords：lasertransmissionwelding,absorbentratio,parametersoptimization,LibSVM

Broadening the minimum thickness of 12Cr1MoV forced post-weld heat treatment

Yin Runbang1, Zhang Tao1, Wang Xue2, Zhang Yongguang1

(1. Dongfang Electric Group Dongfang Boiler Co., Ltd., Deyang 643001, Sichuan, China; 2. Wuhan University, Wuhan 430072, China).p46-54

AbstractIn order to study the feasibility of 12Cr1MoV within 8 mm without post-welding heat treatment, the welding procedure tests were carried out through three welding methods of hot wire TIG, manual TIG and shielded metal arc welding. The mechanical properties, metallographic structure, welding residual stress and durability of the joint were studied and analyzed. The results showed that the 12Cr1MoV welded joints with wall thickness no more than 8 mm could be welded by TIG and low hydrogen shielded metal arc welding without post-weld heat treatment. Through the comparative test, it was proved that it was not necessary to adopt measures of preheating before welding and slow cooling after welding when the post-welding heat treatment of joints with thickness of 8 mm or less was cancelled.

Keywords:boiler,12Cr1MoV,post-weldheattreatment,theminimumwallthickness

Analysis on welding quality problems and causes of crack formation of girth welds in high grade steel pipeline

Li Liang1,2, Huang Lei1,2, Nie Xianghui1,2, Liu Yinglai1,2, Zhang Yi1

(1. CNPC Tubular Goods Research Institute, Xi’an 710077, China；2. Beijing Longshine Oil Tubular Technology Co., Ltd., Beijing 101100, China).p55-60

AbstractPhysical and chemical inspection and defect analysis were carried out on twelve girth welds with cracks of high grade steel pipeline, and the forming mechanism of cracks caused by welding quality problems were studied. The results showed that the overhead welding area of girth welds was the high occurrence area of crack initiation, which accounted for 83.33% in this paper. The tensile strength and Vickers hardness of girth welds met the standard requirements. However, the Charpy impact energy of some girth welds was lower than the standard requirements, and the number of unqualified samples accounted for about 19.44% of the total samples. The main reason for unqualified impact toughness was the insufficient number of welding layers and passes. The main welding quality problems leading to girth weld cracking included four categories, such as inner surface defects of root welding, groove and root incomplete fusion, sulfur segregation in root welding and copper pollution in filling welding groove. The insufficient number of welding layers and passes, the excessive amount of weld misalignment and the superposition of the above defects promoted the formation of cracks.

Keywords:highgradesteel,girthwelds,mechanicalproperties,weldingqualityproblems,causesofcrackformation